Are convection microwave ovens a useful item to have? Or are they not good as a microwave and not good as a convection oven either?
I understand that a regular convection oven helps to cook things faster. But a microwave cooks things pretty darn fast already so why would you want a convection feature?
Microwave: A microwave heats water and molecules in the food by using microwave radiation. It will heat food efficiently and quickly, but does not brown or bake like a conventional oven.
Oven: Fueled by gas or electricity and heats from the bottom (baking, roasting) or from the top (broiling). The heat is from a single direction and not uniform.
Convection Oven: An oven that has a fan that circulates heated air. This allows for operation at a lower temperature while cooking more quickly. It also results in a more even bake.
Convection Microwave (Oven): A combination of a microwave and a convection oven. Allows for even, quick cooking that is browned or baked.
So, at the bottom of the scale is a microwave and an oven. They each have different functions. Then there is a middle tier that would be a convection oven - an improvement over the oven. The top tier is the convection microwave oven that provides all the features: quick cooking, heating, baking, browning, and evenness.
If you do a lot of cooking and only have a single oven, but find yourself wishing you had a second, a convection microwave would be useful for you. If you want something truly multi-purpose, then yes. Since each has a set of features it provides and/or lacks, it comes down to what best fits your needs.
It is a combination of a regular convection oven with a microwave, so you have both hot air and microwaves cooking your food. So the advantage is you get the quick interior heating of the microwaves combined with the surface browning from the hot air; convection just makes that hot air cooking faster and more even.
There is one large con which probably does not affect all brands. I have frequently heard of combos which have a mode which is labeled as "convection only" but they do not turn the microwave off. The results are clearly like microwaved food, and thus they are unsuitable for baking.
I cannot tell you the exact brands and models which have this problem, but for anybody buying such an appliance, I would suggest first to search experience reports about this kind of problem. One of the probable cases turned up here on Seasoned Advice, Why do my pizzas get such hard crusts?, and I seem to remember other question indicating a similar problem, but cannot find them right now.
